Crystal Structure of the KIF5C Motor Domain With ADP

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Contents 1 Function 2 KIF5C Binding to Microtubules 3 Structural States of KIF5C 4 Role of L11 5 Mechanochemical Cycle 6 References

Function

Proteopedia page made by Urvija Rajeshkumar Agrawal to fulfill the credit requirements of BI3323-Aug2025 Structural Biology.

Source - X-ray and Cryo-EM structures reveal mutual conformational changes of Kinesin and GTP-state microtubules upon binding by M Morikawa et. al. ^[1]

KIF5C is a microtubule-based motor protein that moves along MTs using ATP hydrolysis. It preferentially binds GTP-state microtubules (GMPCPP-MTs) over GDP-taxol-MTs, enabling selective axonal entry. Binding to the GTP-state MT induces a strong-binding “rigor” conformation in KIF5C, accelerating ADP release and supporting rapid ATP-dependent motility. Recognition of the GTP-state lattice depends on structural features of tubulin, especially the H4–S5 loop of β-tubulin and H11′ of α-tubulin.

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KIF5C Binding to Microtubules

The KIF5C–MT interface involves three regions: L8, the α4–L11 region, and the C-terminal part of L12 near H12 of β-tubulin. GMPCPP-MTs strengthen these contacts, while GDP-taxol-MTs distort tubulin loops, weakening binding. KIF5C reshapes the MT lattice upon binding, and MT conformation in turn determines KIF5C affinity and ATPase activation.

Structural States of KIF5C

Cryo-EM structures of KIF5C bound to GMPCPP- and GDP-taxol-MTs, and the crystal structure of nucleotide-free KIF5C, reveal nucleotide-dependent rearrangements in switch I, switch II, helix α3–L9, L11, and the neck-linker.

On GMPCPP-MTs:

Switch I (α3–L9) adopts a closed state that facilitates Mg²⁺/ADP release.

Switch II helix α4 rotates toward the MT axis.

L11 elongates and inserts between α4 and α6.

The neck-linker initial segment docks.

These changes define the strong-binding rigor conformation.

Role of L11

Loop L11 is essential for discriminating GTP-state from GDP-state MTs. Replacing KIF5C L11 with KIF1A L11 abolishes GTP-state specificity. Triple alanine mutations reduce but do not eliminate it. L11 is also required for MT-activated ATPase acceleration.

Mechanochemical Cycle

On GTP-state MTs, KIF5C transitions from a weak Mg·ADP state to the rigor conformation upon ADP release, followed by Mg·ATP entry, neck-linker docking, and the power stroke that advances the motor.

References

1. ↑ Morikawa M, Yajima H, Nitta R, Inoue S, Ogura T, Sato C, Hirokawa N. X-ray and Cryo-EM structures reveal mutual conformational changes of Kinesin and GTP-state microtubules upon binding. EMBO J. 2015 Mar 16. pii: e201490588. PMID:25777528 doi:http://dx.doi.org/10.15252/embj.201490588